In an apron conveyor in which powdery or granular material is conveyed along an upwardly inclined path, it is necessary to provide means for preventing the conveyed material from coming out through the gap between the overlapping front and rear end portions of adjacent aprons. Such a means is disclosed in, for example, Japanese Patent Application Laid-open No. 101308/1986, as shown in FIGS. 2(a), 2(b) and 2(c) hereof.
Namely, an apron E is mounted to each link 1a, 1b, . . . of a conveyor chain 1 and comprises bottom plates E1, E2 . . . and outwardly projecting side plates S1, S1, S2, S2 . . . Each link 1a, 1b . . . is pivotably connected with adjacent links by means of connecting pins P. The overlapping front end portion of the bottom plates E1, E2 . . . is formed of a trapezoidal shape so as to have a flat top 2, a proximal end leg 3 and a free end leg 4. On the other hand, the overlapping rear end portion of the bottom plate includes a circular wall 5 which is complimentary to the movement locus of the free end 4' of the end leg 4 as generated about the pivot axis defined by the connecting pin P, a recess 6 adjacent to and above said circular wall 5, and an upright free end 7.
When the links 1a and 1b are straight as shown in FIG. 2(a) with no bending angle about the connecting pin P on a conveying path having an angle of inclination .alpha., the forward end 4' of the front overlapping end portion of the apron's bottom plate E2 is in contact with the forward end of the circular wall 5 of the forward apron E1. Thus, downward entering of the conveyed material from the forward apron E1 into the space 8 formed by the respective overlapping end portions of the forward and rearward aprons as mentioned above may be prevented. And when the links 1a and 1b make an angle .beta. as shown in FIG. 2(b), the forward end 4' of the front overlapping end portion of the bottom plate E2 is adapted to make a sliding contact with the outer surface of the circular wall 5 about the connecting pin P until it reaches the other end of the circular wall 5; and accordingly, no gap may be created between the forward end 4' and the circular wall 5 which many allow the conveyed material to enter thereinto. Should a small amount of the material enter the space 8, it will be held in the recess 6 and is incapable of going over the upright free end 7.
As the bending angle increases to .gamma. as shown in FIG. 2(c) so that the forward link 1a becomes substantially horizontal, the forward end 4' of the overlapping end portion of the bottom plate E2 is separated from the circular wall 5 and the space 8 is opened. However, since the forward bottom plate E1 is almost horizontal, there is no fear that the conveyed material enters the space 8 from the forward bottom plate E1. And as the forward link 1a further advances so as to incline downward, the material which may have accumulated in the space 8 may be discharged onto the forward bottom plate E1.
In the aforementioned prior art, the forward end 4' formed in the front overlapping end portion of the bottom plate is forced to make a sliding contact with the circular wall 5 formed in the rear end portion of the adjacent bottom plate, thus jamming the material in the gap as the relative bending of the links takes place, which causes wear of the sliding portions. This can cause the gap between the forward end 4' and the circular wall 5 to become larger, which in turn makes it easy for a larger amount of material to pass through the gap. Therefore, complete prevention of leakage of the conveyed material is not possible by the above-mentioned prior art.
Accordingly, this invention relates to an apron-type conveyor which is believed to significantly improve upon and overcome the deficiencies of the prior art conveyor.